Pityriasis Rotunda

Etiology

No established etiology for pityriasis rotunda exists. Authors have attached it to various disorders of keratinization, such as ichthyosis vulgaris, late-onset congenital ichthyosis, and acquired ichthyosis. Type I pityriasis rotunda, also known as paraneoplastic pityriasis rotunda, primarily appears in conjunction with hepatic and gastric malignancies, but it can also manifest in the following malignancies:

• Immunoglobulin G myeloma, multiple myeloma
• Acute myeloid leukemia
• Chronic myeloid leukemia
• Adenocarcinoma of the prostate
• Esophagus carcinoma
• Gastric carcinoma
• Squamous cell carcinoma of the palate

Pityriasis rotunda is also linked to several systemic diseases, including:

• Malnutrition
• Diabetes mellitus
• Infections (tuberculosis, leprosy, and osteitis)
• Hepatic diseases such as cirrhosis and hepatitis C virus [5]
• Chronic obstructive pulmonary disease and recurrent pulmonary infections
• Heart disease
• Female genital tract anomalies (ovarian cysts and fibroids)
• Glucose-6-phosphate dehydrogenase deficiency (favism)
• Chronic diarrhea
• Scleroderma
• Sarcoidosis
• Hormonal disorders such as hyperprolactinemia
• Acquired immune deficiency syndrome [6]

However, researchers have not eliminated the idea that the association of some of these conditions associated with pityriasis rotunda, especially favism, could be due to chance.[7][8][9][10]

Epidemiology

Pityriasis rotunda affects all sexes equally, although certain authors noticed a slight predominance in women. The age for the diagnosis ranges from 20 to 45 years, with extremes of 2 and 87 years. There is a particular racial and geographic distribution for pityriasis rotunda. Most cases are reported in Japan and among West Indian and Black individuals in South Africa. Case reports of pityriasis rotunda in Black Americans are less common, and the frequency of the disease on the North American continent is not known. Cases of pityriasis rotunda among White individuals are also rare. Familial cases may also be observed and likely have a hereditary determinism, which may be an autosomal dominant transmission. Researchers have documented a familial incidence among 42 individuals in Sardinia, thereby corroborating the theory of genetic influences.[7] A small number of cases involving children have also been documented.[1][11]

Researchers have developed a categorization encompassing all known pityriasis rotunda cases, proposing 2 subcategories. The first group consists of Asian or dark-complected patients with less than 30 hyperpigmented lesions. This condition does not run in families and is linked to 30% of cases of cancer or systemic diseases. White patients with a familial history manifest the second kind; additionally, the lesions are typically hypopigmented and numerous (>30), and this subtype is not associated with a chronic condition. This subtype emerges between ages 25 and 45 and remains constant throughout life.[12]

Pathophysiology

Lesions of pityriasis rotunda occasionally manifest disturbance of the epidermal filaggrin.[9] Hashimoto et al described a diminished expression of loricrin and filaggrin in pityriasis rotunda lesions.[13] Yoneda et al reported a complete absence of the profilaggrin-N terminus domain in the lesional skin.[14] Further, Makino et al reported a decrease in the expression of epidermal filaggrin 2, as seen in ichthyosis vulgaris, atopic dermatitis, and psoriasis vulgaris.[9]

Histopathology

The histopathology of pityriasis rotunda lesions can reveal various findings, such as hyperkeratosis, which is primarily orthokeratotic but also parakeratotic. Plugs are observed within hair follicles, elongated rete ridges, a diminished or absent stratum granulosum, slight spongiosis, enhanced pigmentation of the basal layer, pigmentary incontinence, and perivascular infiltrate of small lymphocytes. Periodic acid-Schiff stain for fungus is negative. These changes are similar to those observed in ichthyosis vulgaris. Type I pityriasis rotunda may be a biological variation of paraneoplastic ichthyosis vulgaris.[4] 

Grimalt et al performed an ultrastructural study on pityriasis rotunda lesional skin biopsies. They noted the existence within the epidermis of vacuoles containing lipids and crystal-like inclusions. The granules of keratohyalin remained normal, while the number of keratinosomes increased. The stratum granulosum was reduced to a single layer. The cementing substance connecting corneocytes was abundant. These findings indicate a stronger relationship between pityriasis rotunda and congenital ichthyosis than with ichthyosis vulgaris.[15]

History and Physical

The diagnosis of pityriasis rotunda is usually based on clinical examination. Skin lesions are generally asymptomatic or mildly symptomatic. Pityriasis rotunda plaques are scaly, dry, sharply defined, and round, with prominent hair follicles but no inflammatory erythema. Scales may be highlighted by scratching the plaques. The lesions appear hypopigmented in fair-skinned patients and hyperpigmented in dark-skinned patients. The plaques of pityriasis rotunda may be confluent; coalescence of lesions may result in a polycyclic formation. Their size is variable (1 cm to more than 20 cm), and their number ranges from 1 to dozens but rarely exceeds 100. Pityriasis rotunda affects mainly the trunk (back and abdomen), buttocks, and proximal parts of the limbs (thighs and arms)(see Image. Pityriasis Rotunda). The face, hands, and feet are usually not involved. Some patients may exhibit associated skin lesions of ichthyosis vulgaris. A familial history of ichthyosis vulgaris has been reported in certain patients with pityriasis rotunda.[16][17]

Grimalt et al proposed a classification of pityriasis rotunda. The first subtype comprises less than 30 hyperpigmented patches, mainly in Black and Asian persons. No similar familial cases are seen in this subtype, but associated diseases are frequently described, such as malignancies (solid tumors and hemopathies), systemic diseases, and infections. A second subtype is characterized by more than 30 hypopigmented patches, occurring mainly in white patients with a familial history of similar skin lesions. There usually is no underlying disease. This classification is schematic since overlap cases have been reported.[15]

Evaluation

The diagnosis relies on clinical suspicion.[18] Mycological examination of scaly material removed from lesional skin (direct microscopy using potassium hydroxide and fungal culture) is useful in ruling out dermatomycosis. Wood light examination is used if erythrasma is suspected. On dermoscopy, white polygonal streaks with a homogeneous brown background were observed. The polygonal scales over clearly defined pigmented brown patches represent hyperkeratosis and a pigmented basal layer in histological analysis, respectively.[1][19]

Treatment / Management

Management of pityriasis rotunda is often challenging. Topical corticosteroids, antifungal agents, emollients, tars, and keratolytic topicals (salicylic acid and lactic acid) have proven ineffective; retinoids, topical (retinoic acid and tazarotene) or oral (etretinate), have been used with little or no success in pityriasis rotunda. Treatment with vitamin D3 analogs such as calcipotriol leads to a progressive improvement in the lesions in a few patients. However, for patients with comorbidities, successful treatment of the underlying disease often leads to remission of pityriasis rotunda lesions.[18]

Differential Diagnosis

Annular lesions are ring-shaped formations that arise from macules, papules, or plaques. While the annular pattern typically indicates lesion enlargement, annular lesions may not continue to expand. Various subtypes of annular lesions can be identified. These subtypes encompass a diverse array of inflammatory and infectious dermatoses, including:

• Erythrasma
• Leprosy
• Parapsoriasis
• Pityriasis alba 
• Pityriasis rosea
• Plaque psoriasis
• Sarcoidosis
• Tinea corporis
• Tinea cruris
• Tinea versicolor
• Elastosis perforans serpiginosa
• Nummular eczema
• Early-stage mycosis fungoides
• Fixed drug reaction
• Figurate erythema

Prognosis

Once lesions manifest, they typically remain static throughout life unless the underlying internal disease or malignancy is managed, resulting in resolution or improvement. Moreover, childhood-onset has been associated with a more favorable prognosis, with remission occurring in nearly 50% of cases throughout later childhood.[11] Pityriasis rotunda was associated with a quantitatively and statistically significant reduction in mortality risk among all documented skin abnormalities of hepatocellular carcinoma.[20]

Complications

The manifestation of pityriasis rotunda in an older adult, without a familial history of the disorder, is significantly correlated with an underlying malignancy.[4]